In recent years, fuel saving characteristics of vehicles are again regarded as important, as the global environmental issues are drawing more attention. As for the global environmental issues, measures need to be promptly taken against global warming. Vehicles with gasoline engines that emit greenhouse gases such as carbon dioxide have been repeatedly improved, fuel efficiency is enhanced, and discharged greenhouse gases are reduced.
An electric vehicle using, as a driving source, a motor having higher energy utilizing efficiency than that of a gasoline engine, and a hybrid car using both a gasoline engine and a motor as driving sources are developed, and the fuel saving characteristics of vehicle are enhancing for sure.
However, no matter how high the original fuel saving characteristics of the vehicle are, if a driver's driving manner is against the fuel saving, e.g., if the operation of an accelerator is unsuitable and an engine braking is not effectively utilized, the high fuel saving characteristics of the vehicle would be meaningless. To address this issue, conventional technologies have been devised to prompt the driver to operate the accelerator in an appropriate manner so as to effectively utilize the engine braking, and to give notification to the driver to encourage the fuel-saving driving.
According to one of the conventional technologies for example, operation time of engine braking and operation time of an auxiliary brake (normal disk or drum brake) during the driving operation were recorded, and the fuel saving driving by a driver was rated based on a ratio of the operation time of the auxiliary brake to the operation time of the engine braking. The driver is informed of a rating result and prompted to operate the accelerator such that the engine braking is effectively utilized with the least use of the auxiliary brake.